Amid historically low natural gas prices and the warmest March ever recorded in much of the United States, coal's share of total net generation dropped to 34%—the lowest level since at least January 1973 (the earliest date for which EIA has monthly statistics). Despite seasonally low loads, natural gas-fired generation grew markedly and accounted for 30% of overall net generation by March 2012 (see chart above). Total electricity demand fell this winter as warmer weather reduced home heating requirements.

Coal generation decreased 29 billion kilowatthours from March 2011 to March 2012, while natural gas generation increased 27 billion kilowatthours during the same time period. In March 2012, coal's share of total generation was 34% compared to natural gas at 30%.

Natural gas prices were near 10-year lows this winter, leading the generators in some states (such as Ohio and Pennsylvania) to increase their dispatch of natural gas-fired plants. Newer vintage natural gas-fired units operate at higher efficiency than older, fossil-fired units, which increases the competitiveness of natural gas relative to coal.